Human blood vessels often become occluded or blocked by plaque, thrombi, other deposits, or emboli which reduce the blood carrying capacity of the vessel. Should the blockage occur at a critical place in the circulatory system, serious and permanent injury, and even death, can occur. To prevent this, some form of medical intervention is usually performed when significant occlusion is detected.
Balloon angioplasty and other transluminal medical treatments are well-known and have been proven efficacious in the treatment of stenotic lesions in blood vessels. The application of such medical procedures to certain blood vessels, however, has been limited, due to the risks associated with creation of emboli during the procedure. For example, angioplasty is not the currently preferred treatment for lesions in the carotid artery because of the possibility of dislodging plaque from the lesion, which can enter the various arterial vessels of the brain and cause permanent brain damage. Instead, surgical procedures such as carotid endarterectomy are currently used, wherein the artery is split open and the blockage removed, but these procedures present substantial risks of their own.
Other types of intervention for blocked vessels include atherectomy, deployment of stents, introduction of specific medication by infusion, and bypass surgery. Each of these methods are not without the risk of embolism caused by the dislodgement of the blocking material which then moves downstream. In addition, the size of the vessel may limit access to it.
There is also a need to efficiently remove occlusions from a patient without excess undesired removal of native blood and tissue within the system. Constant flow suction or vacuum pressure is effective at removing freed or dislodged occlusions, but typically remove unnecessary amounts of blood in the process. Thus, there is a need for a system to effectively contain and remove such emboli without undesired consequences, such as excess removal of blood and tissue from the vessel.
Vessels as small as 3 mm in diameter are quite commonly found in the coronary arteries, and even certain saphenous vein graph bypass vessels can also be as small as 3 mm or 4 mm; although some can range as high as 7 mm. Certain of the carotid arteries also can be as small as 4 mm in diameter; although, again, others are larger. Nevertheless, a successful emboli removal system must be effective within extremely small working areas.
Another obstacle is the wide variety in emboli dimensions. Although definitive studies are not available, it is believed that emboli may have approximate diameters ranging anywhere from tens of micrometers to a few hundred micrometers. More specifically, emboli which are considered dangerous to the patient may have diameters as large as 200 to 300 micrometers or even larger. Thus, an effective emboli removal system must be able to accommodate relatively large embolic particles and, at the same time, fit within relatively small vessels.
Another difficulty that must be overcome is the limited amount of time available to perform the emboli removal procedure. That is, in order to contain the emboli produced as a result of intravascular therapy, the vessel must be occluded, meaning that no blood perfuses through the vessel to the end organs. Although certain perfusion systems may exist or may be developed which would occlude emboli while permitting the substantial flow of blood, at present, the emboli may be contained only with a complete occlusion as to both blood flow and emboli escapement. Thus, again depending upon the end organ, the complete procedure, including time for the therapeutic treatment as well as exchanges of angioplastic balloons, stents, and the like, must be completed within a short time. Thus, it may be difficult to include time for emboli removal as well. This is particularly true in the larger size vessels discussed above wherein a larger volume results in additional time required for emboli evacuation.
Additionally, there has been a long felt an unmet need to provide a catheter that is adept at removing harder material, such as calcium (e.g. harder than thrombus and plaque). Cutting and removal of such harder materials generally requires additional procedure time and increased risks.
Moreover, it is important that an emboli containment and removal system be easy to use by physicians, and compatible with present therapeutic devices and methods.